1. Field of the Invention
This invention relates to a recording method, a recording apparatus for conducting the recording method and an ink jet cartridge for use in the recording apparatus.
2. Related Background Art
It is known to use a reticulated or felted foam of typical polyether-type polyurethane foam (ink absorbent member) as an ink reservoir in some cartridges for ink jet recording, as disclosed in Japanese Patent Application Kokai (Laid-open) No. 64-26452. However, the foam has a possibility to contaminate the ink or to adversely effect the flowing characteristics of the ink, when used as an ink reservoir in the ink jet cartridge, owing to the remaining impurities in the foam. The above-mentioned Japanese Patent Application Kokai (Laid-open) No. 64-26452 discloses a method for determining the cleaning degree of foam, and Japanese Patent Application Kokai (Laid-open) No. 64-26453 (=corresponding to U.S. Pat. No. 4,824,887) discloses an apparatus for cleaning the foam. That is, the former prior art reference teaches control of an amount of involatile residues in a cleaned foam to less than 0.2% by weight on the basis of the foam and also control of a surface tension of an ink stored in the foam to a surface tension change rate of more than 40 dynes/cm or less than 7 dynes/cm. The latter prior art reference teaches an automatic system for-removing contaminants through a recyclic, closed loop using Freon 113 as a solvent on the basis of such a concept that only rinsing of a foam with a solvent provides unsatisfactory washing. However, both of these prior art references are directed only to washing of involatile residues as a cause for clogging the discharge outlet from the foam.
Since the ink absorbent member is used as encased in an ink cartridge, the ink absorbent member has been so far prepared by hot pressing an ether-type foaming polyurethane in most cases. That is, the foaming polyurethane is sliced to a desired thickness and then is converted to a continuous foam body through a known film-forming process, followed by hot pressing at a high temperature such as 190.degree. to 210.degree. C. and cutting to a predetermined size to obtain ink absorbent members. The rigidity of the ink absorbent member can be improved by the hot pressing thereby facilitating its insertion into an ink tank and eliminating vibration of the ink absorbent member in the ink tank to stabilize ink feeding to the discharge outlet.
When the ink absorbent member is used directly after the hot pressing, impurities contained in the ink absorbent member are dissolved into the ink to lower the printing quality. According to the conventional practice, the ink absorbent member is washed with a halocarbon-based solvent such as Flon after the hot pressing and dried, and then provided in an ink tank to subject the ink absorbent member to ink impregnation and absorption.
In order to prevent volatilization and evaporation of the ink, the ink cartridge using such an ink absorbent member is packaged in a gas-tight container one by one. Furthermore, in order to prevent an ink leakage, all the openings open to the outside are pasted with a sealing member such as a seal tape to completely cover the entire openings. Gas tightness is further ensured by providing a cap having an elastic member onto the sealing member. The elastic member includes, for example, rubber, etc.
However, the above-mentioned prior art has such disadvantages as a necessity for a special washing apparatus because the foam is washed with a highly volatile, Flon-based solvent having a harmful effect on the environment, and a high possibility for an adverse effect on recording when the even a trace amount of Flon-based solvent remains in the foam owing to poor compatibility with the ink, though the Flon-based solvent is used only for the washing purpose.
Furthermore, the washing degree is evaluated in the prior art by determining involatile impurities as weight of dry extract on the basis of weight changes of foam, and thus the exactness and reproducibility of measurements are not satisfactory owing to high hygroscopic properties of foam itself and impurities themselves, and it is quite difficult to obtain foams with a satisfactory cleaning degree. Furthermore, since the involatile impurities are defined in the prior art merely as weight of dry extract, it is not clear what the individual impurities really are, and thus it is quite difficult to conduct an efficient and effective control of essential substances as main factors. Thus, there are large fluctuations in the evaluation of the cleaning degree of foams even in the prior art and there are problems in constant supply of highly reliable products.
Moreover when an ink is caused to leak from the ink jet cartridge for some reason during the handling of ink jet cartridge, the leaked ink fouls the ink jet cartridge, because the rubber cannot absorb the ink, and sometimes flows to electrical contacts to cause a contact failure.
The present inventor thus studied use of materials capable of absorbing an ink as the elastic member. As the materials capable of absorbing the ink, foamed polyurethane containing foams in a fine continued cell structure was found preferable, and thus the present inventor studied use of ester-type foamed polyurethane prepared by polymerization of polyesterpolyol with diisocyanate according to a known process. However, the present inventor found that, when the ester-based foamed polyurethane was used as an elastic member for the ink jet cartridge cap, the foamed polyurethane deteriorated, if preserved for a long time such as one month or more, particularly at a high temperature, for example, about 60.degree. C., and the foamed polyurethane lost elasticity and failed to press the sealing member. Furthermore, the water absorbability was lowered causing to cause an ink leakage.